Source-insulator interaction in high-voltage pollution tests

This work develops a digital-computer simulation of the interaction between an artificially polluted insulator and a high-voltage direct-current (HVDC) or an alternating-current (AC) source configuration.The polluted-insulator model includes conditions for the existance of arcs on contaminated surfaces; arc motion, speed of arc propagation, and arc reignition criteria; and thermodynamic phenomena in an unbridged wet layer. The effect of the source parameters on the leakage current waveform, the dynamic voltage drop and the critical flashover voltage is systematically investigated and supported by experimental results. The simulation results are used to establish the HV test source requirements and provide guidance for the design of the test source.For an AC source, it is important to consider the equivalent shunt capacitance in addition to the short-circuit current and the transformer reactance/resistance ratio when interpreting pollution test results. The use of series capacitance to compensate for a weak source is also considered.In the case of a DC source, the mean voltage drop during a critical leakage current impulse proves to be a better indicator of the error in the measured critical voltage. The studies are extended for the DC source configurations most commonly used by power utilities today